PRACTICAL 3 : UNIFORMITY OF WEIGHT OF TABLETS AND CAPSULES

Objectives

1. To test the uniformity of weight of tablets and capsules
2. To ensure the consistency of dosage unit

Introduction

        To ensure the consistency of dosage units, each unit in a batch should have a drug substance content within a narrow range around the label claim. Dosage units are defined as dosage forms containing a single dose or a part of a dose of drug substance in each unit. The uniformity of dosage units specification is not intended to apply to suspensions, emulsions, or gels in unit-dose containers intended for topical administration. The term “uniformity of dosage unit” is defined as the degree of uniformity in the amount of the drug substance among dosage units. Therefore, the requirements of this chapter apply to each drug substance being comprised in dosage units containing one or more drug substances, unless otherwise specified in the individual monograph. The uniformity of dosage units can be demonstrated by either of two methods, Content Uniformity or Weight Variation.

Procedures

Tablets

1. 20 tablets are weighed. The average weight was determined.

2. Then, tablets was weighed individually and for each tablet, the percentage of deviation of its weight from the average weight was determined

3. The deviation of individual weight from the average weight should not exceed the limits given below.

The percentage of deviation is calculated using the formula as below.

Capsules

1. 20 capsules are selected at random.

2. One capsule was weighed. The capsule was opened and the contents are removed as

completely as possible. The emptied shells are weighed. The net weight of its contents are

determined, that is by subtracting the weight of shells from the weight of the intact capsule.

3. The procedure are repeated with another 19 capsules.

4. The average net weight are determined from the sum of individual net weights.

5. The percentage of deviation from the average net weight for each capsules are determined.

The deviation of individual net weight should not exceed the limits given below. 

The percentage of deviation is calculated using the formula as below.

Results

Tablets

Capsules

Calculations

1. Average weight of tablet        

=  Total weight of 20 tablets

                         20

= 13677.1

                    20

                ≈  683.9 mg

2. Average net weight of capsule

                =  Total net weight of 20 tablets

                         20

                =  296.3 mg

Discussion

                Based on the experiment, the uniformity of weight was determined by using tablets and capsules in order to make sure that  the dosage units is consistent. From the result obtained, the tablets used has an average weight of 683.9 mg which is under  the category of ‘250mg and more’. All the 20 tablets that have been carried out did not exceed  the limit of + 5.0% and therefore, they are considered to pass the test. For the capsules, all 20 capsules have average net weight of 296.3 mg. Therefore, it is under  the category of  ‘300mg and above’ category. All the capsules have the percentage of deviation within the + 7.5%, which did not exceed the limitation,  so, all of the 20 capsules pass the test.

Conclusion

        From this experiment, the percentage deviation from the average weight does not exceed the limitation. So, all the 20 tablets and capsules have uniform weight, which obey the standard properties required.

References

1. http://www.drugfuture.com/pharmacopoeia/usp32/pub/data/v32270/usp32nf27s0_c905.html
2. http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/2011-02-25905UNIFORMITYOFDOSAGEUNITS.pdf